Pretty much on your race to hit level 70 you should get this.
This is 500,000 gold PICKED UP. What's important about this is selling items, and completing quests, do not work for this. The best thing to do is kill elites and open chests when you can. The higher your level the more money will drop. At level 45-50 I was able to get about 100k in about an hour or two. . At level 1-20 it took me many hours. So the best thing to do is focus more on your level then what is dropping.